X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from relay02.roc.ny.frontiernet.net ([66.133.182.165] verified) by logan.com (CommuniGate Pro SMTP 4.3.2) with ESMTP id 963984 for flyrotary@lancaironline.net; Thu, 26 May 2005 10:57:34 -0400 Received-SPF: pass receiver=logan.com; client-ip=66.133.182.165; envelope-from=canarder@frontiernet.net Received: from filter08.roc.ny.frontiernet.net (filter08.roc.ny.frontiernet.net [66.133.183.75]) by relay02.roc.ny.frontiernet.net (Postfix) with ESMTP id 759FB37003F for ; Thu, 26 May 2005 14:56:50 +0000 (UTC) Received: from relay02.roc.ny.frontiernet.net ([66.133.182.165]) by filter08.roc.ny.frontiernet.net (filter08.roc.ny.frontiernet.net [66.133.183.75]) (amavisd-new, port 10024) with LMTP id 14257-06-73 for ; Thu, 26 May 2005 14:56:50 +0000 (UTC) Received: from [127.0.0.1] (67-137-69-152.dsl2.cok.tn.frontiernet.net [67.137.69.152]) by relay02.roc.ny.frontiernet.net (Postfix) with ESMTP id E1546370051 for ; Thu, 26 May 2005 14:56:49 +0000 (UTC) Message-ID: <4295E3AF.6040809@frontiernet.net> Date: Thu, 26 May 2005 09:56:47 -0500 From: Jim Sower User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7) Gecko/20040514 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Amps consumed data References: In-Reply-To: Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit X-Antivirus: avast! (VPS 0521-3, 05/26/2005), Outbound message X-Antivirus-Status: Clean X-Virus-Scanned: by amavisd-new-20040701 (2.0) at filter08.roc.ny.frontiernet.net Finn Lassen wrote:

Yes, you'll need a relay in series with the "fat" wire, IF you have an internally regulated alternator that does NOT stop putting out voltage when the "thin" wire is disconnected. Looks like Bernie's alternator will not need that relay. No need to introduce an unneeded additional component - another point of possible failure.
According to Nuckolls, even alternators with external regulators can run away and that's why he recommends the crowbar OV protector. Disconnecting the "thin" wire won't always stop the alternator from putting out. You have to disconnect the "fat" (B+) line to be assured of an end to an over voltage condition ... Jim S.
Finn

Jim Sower wrote:
Finn Lassen wrote:
The small wire goes to its separate circuit breaker. The crowbar is connected to this wire (and ground).
When the crowbar circuit senses an over-voltage, it clamps that wire to ground (and pops the circuit breaker).
Only works on your kind of alternator that stops putting out voltage on the fat wire when it doesn't get voltage in on the "thin" wire. I have an internal regulator, so all I have is a "fat" (B+) wire. I jump the B+ terminal of the Alt to the "F" terminal with a couple inches of 17 ga wire. I connect and disconnect the B+ to the rest of the airplane with a "master" relay powered by the Alt switch on the panel and protected by Nuckolls' crowbar. In an over voltage situation, the relay opens. The Alt is disconnected from the airplane and I could care less what the voltage is. As someone else asked, does it really stop putting out voltage on the fat wire - easily measured on the fat wire with a voltmeter - voltage should drop to maybe 13.2 V as opposed to the 15 - 16 Volts when alternator is delivering power.

Finn

WALTER B KERR wrote:
 Are you saying that you are running an internally regulated, 
'one-wire' 
alternator & you were measuring current, not voltage? If so, the 
current 
measurement dropping to zero when you break the B-lead doesn't mean 
the 
alternator isn't 'putting out.' There won't be any current flowing 
because the circuit is no longer complete, but the alternator can 
still 
be producing voltage potential at the B-lead terminal. The only way 
to 
tell is to have a volt meter hooked directly to the B-lead terminal 
when 
you open the B-lead. Same idea as an electrical outlet in your 
house: 
120 VAC al the time but no current until you plug something in & 
turn it on.

The aeroelectric list hand-wringing about 'load dump' should only be 

relevant if you lose the connection to the *battery*. If the 
regulator 
fails & allows unregulated output from the alternator then the 
B-lead 
overvoltage disconnect relay described in the 'Connection' is what 
prevents the high voltage from damaging the a/c electronics. By the 
time 
you get to this point, 'load dump' is meaningless because the result 
of 
load dump (overvoltage) has already happened & preventing load dump 
is 
no longer an issue.

We'll talk when you get here on Friday.

Charlie

    
---------------------------------
Maybe I misled you. There are 2 wires hooked to the alternator. Only one
wire of the 3 on the plug, but the heavy wire going to the battery is
where I measured current. Are you saying I should measure the voltage on
the small connector wire?

I'm sure you can straighten me out this week end when we're are talking.

Thanks
Bernie

  
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